In other developments, Racing NSW issued a "show cause" ­notice to Weir, requesting the ­embattled trainer justify why his horses should be allowed to run in the Golden Slipper and The Championships in Sydney after the discovery of the illegal jiggers, some allegedly found in a safe on a Weir property.

Racing NSW chief executive Peter V'landys said: "It is critical that the image, interests and ­integrity of thoroughbred racing in NSW are not compromised while Mr Weir's conduct is ­further investigated." Weir is the ­nation's most successful trainer.

Weir, 48, boasts an Australian ­record of 491 wins and more than $31 million in prizemoney last season.

His stables in Warrnambool and Ballarat were raided at dawn on Wednesday, plunging his career into crisis.

Four tasers, or jiggers, an unlicensed firearm and a small substance suspected to be cocaine were allegedly seized in the raid.

Leading Victorian trainer Tom Dabernig said Weir's achievements should be looked at, including Prince Of Penzance's Cup success.

"Occasionally, long shots do get up though, it's a very hard thing to accuse people," he said. "But under these circumstances it would make you question some of the recent ­results over the last few years."

Dabernig and other top trainers are believed to have approached RV's integrity staff to seek clarification on the ­appropriateness of Weir ­continuing to train.

Michelle Payne denied any knowledge or involvement of any illegal practices during her time training with Weir.

"I haven't been part of the stable for the past 18 months since taking out my training licence and going separate ways from Darren Weir's stables," she said.

The Coalition for the Protection of Race Horses called for an inquiry into the sport amid industry concerns over Prince Of Penzance's win. "This matter brings into questions the result of the 2015 Melbourne Cup," said Elio Celotto of the coalition.

Prince Of Penzance wore blinkers when he upstaged quality opposition to win the Cup. "The winner trained by Weir had quite an ordinary racing record by Cup standards leading into the Cup and certainly after," he said.

RV said while it was unable to provide ­detail on the probe, authorities were not looking at the 2015 Melbourne Cup.

Investigations are understood to focus on the use of electric shocks and strikes with a whip to horses as they run on the treadmill while wearing blinkers.

It is alleged blinkers are then put on the horse on race day so they associate the blinkers and whip with the memory of electric shock, and run faster.